The present invention relates to a high self resonant frequency multilayer inductor and method for making same.
All inductors have a self resonant frequency. The self resonant frequency is determined by an inverse relationship between the inductance of the coil and the residual capacitance of the inductance coil. As the residual capacitance increases, the self resonant frequency decreases. It is important to have a self resonant frequency as high as possible because this allows the inductor to operate at a higher frequency. Consequently, in order to maximize the self resonant frequency, it is desirable to reduce the residual capacitance within the inductor.
FIGS. 2 and 4 show a typical prior art inductor 10. Inductor 10 includes two end terminations 12, 14 which are secured over the opposite ends of a coil assembly 16. Referring to FIG. 4, the coil assembly 16 includes a top coil layer 18, a plurality of intermediate coil layers 20, and a bottom coil layer 22. The coil layers 18, 20, and 22 are vertically spaced apart from one another and a dielectric 24 fills the spaces between the various layers 18, 20, 22. Via openings 26 in the dielectric are filled with conductive via fills 28 which connect the various coil layers 18, 20, 22 in series with one another to form a multi turn inductance coil.
The top coil layer 18 is in electrical contact with end termination 14 by means of a top coil layer connection 30. The bottom coil layer 22 is in electrical contact with the end termination 12 at the bottom coil layer connection 32.
There are two kinds of capacitance which are inherent in the arrangement shown in FIG. 4. Between each coil layer 18, 20, 22 there is a capacitance designated by the numeral 34. The capacitances between each of the layers are in series with one another.
In addition to the series capacitances 34 there are a plurality of parallel capacitances designated by the numeral 36 between the outer most edges of each coil layer 18, 20, 22 and the terminations 12, 14.
Therefore, a primary object of the present invention is the provision of an improved high self resonant frequency multilayer inductor and method for making same.
A further object of the present invention is the provision of an improved inductor and method for making same which results in an increase in the self resonant frequency over prior art inductor designs.
A further object of the present invention is the provision of an improved inductor and method for making same which reduces the capacitance between the coil layers of the inductor and the terminations.
A further object of the present invention is the provision of an improved inductor and method for making same which results in a more reliable method of making contact between the ends of the inductor coil and the terminations.
A further object of the present invention is the provision of an improved inductor and method for making same which optionally eliminates the dipping process for creating solder terminations as done previously in prior art devices.
A further object of the present invention is the provision of an improved inductor and method for making same which results in the ability to make smaller parts.
A further object of the present invention is the provision of an improved inductor and method for making same which optionally eliminates the need for grinding or buffing rough edges at the sides of the inductor as was necessary in the manufacture of prior art inductor designs.
A further object of the present invention is the provision of an improved inductor and method for making same which decreases the labor costs, increases the manufacturing yield, and increases the reliability of the part.
A further object of the present invention is the provision of an inductor and method for making same which is efficient, durable, and simple to manufacture.